The US Senate has approved a bill that would require vehicles sold in the US to burn 30% less fuel by the year 2020.
The bill will reduce the amount of petrol vehicles burn
Fuel efficiency will have to be 35mpg. The measure is part of a wider draft law on conserving energy and promoting alternative fuels.
For the first time the fuel requirement would apply equally to cars and sports utility vehicles (SUVs).
If it becomes law, the bill will be the first efficiency increase imposed on US carmakers for nearly 20 years.
It was added to the bill after a compromise was reached with senators who wanted less stringent standards.
The bill was passed without any debate.
The automotive industry had lobbied against the original tougher specifications.
"If we're really smart we'll find a way to make this new approach to fuel efficiency work... for domestic auto companies, their shareholders, their employees and our nation to reduce our dependence on foreign oil," said Sen Thomas Carper, one of the sponsors of the plan.
The bill also requires carmakers to produce more vehicles by 2015 that can run on fuel that is 85% ethanol.